Technical Abstract:
This article is a commentary on a paper in the same journal that criticizes the recent National Breastfeeding Awareness Campaign. That criticism is based on the premise that breastfeeding has not been proven to be of significant public health benefit. The commentary discusses differences in research methodology that have resulted in apparently conflicting findings regarding risk reduction for specific adverse outcomes. Discrepancies frequently arise not only from failure to consider confounding variables, as emphasized by Wolf, but also from failure to adequately characterize both the exposure variable (infant feeding) and the outcome variable (illness). As a general rule, "benefits" of breastfeeding accrue in a dose-response relationship, with the greatest reduction in risk associated with long-term, exclusive breastfeeding. Those studies that do not examine this category of breastfeeding tend to report less significant risk reductions. Precise descriptions of outcome variables is equally important because a) it is often the severity of an illness rather than the incidence that is impacted by type of infant feeding, and b) some illnesses are actually complex or multiple syndromes in which only one or a few of the components may be impacted by infant feed type. At the same time, much of the difference in health outcomes between breast- and formula-fed infants is unexplained and may be the result of residual confounding. More research is needed to identify biological mechanisms that will allow formulation of plausible, testable hypotheses regarding the mechanism of action of human milk components. The commentary discusses some of the specific milk components that have been directly linked to reduction in childhood illness as well as differences in the concentrations of these components in milks from different women. The commentary also stresses the need to promote cultural support for women who choose to breastfeed rather than operating under the assumption that maternal choice alone is responsible for the relative low rates of breastfeeding in the United States.